1. Field of the Invention
The present invention relates to a version control system for software development.
2. Description of the Prior Art
When developing software, it is often important to keep track of changes made to source code. Small changes in the source code to fix bugs or make improvements can unexpectedly lead to large problems. Often, seemingly small changes lead to unexpected problems. Accordingly it is often necessary to keep track of revisions of source code. Version control systems provide tools to record the changes made by developers. The changes between revisions are often called deltas. It is convenient to store one full copy of a file along with the deltas required to reconstruct subsequent versions. Reverse-Delta storage is often used in order to allow the most recent versions to be accessed the fastest. Reverse-delta storage involves storing the full copy of the most recent version along with the changes required to obtain older versions. The changes from the most recent version to older versions are called reverse deltas since they are essentially the opposite of the changes made during development.
In large scale software development, multiple developers work on the same software project. They are each able to modify the files that make up the software project. There is a need for a system to manage the changes made by different developers to avoid conflicts.
Some version control systems, such as RCS (Revision Control System), provide a locked checkout mechanism to control access to files. A developer can checkout a file from a repository with a lock. After the file is locked, no other developer can modify the file. Only the developer who owns the lock can modify the file by checking in a new version.
Often developers are located in geographically separated areas connected by wide area networks yet still need to collaborate on the same software project. U.S. Pat. No. 5,675,802, teaches a geographically distributed version control system. The system has multiple development sites and uses replicas on each site. Access control is provided through mastership rules which govern the ability of each site to modify branches. A particular site can be the master of a particular branch. That site then holds the authoritative revision of that branch. The mastership rules prevent users at other sites from modifying their local copy of that branch. However, configuring and maintaining the mastership rules is an inconvenience for users. Furthermore, the rules must be evaluated for each revision, which can be computationally costly in certain environments. Moreover, the authoritative version of the system is spread among many locations. Accordingly, this type of system requires changes to be merged together at each location to ensure that all sites have up to date copies. This merging is sometimes computationally expensive, and typically requires human intervention to indicate that a merge should occur. In some cases, further human intervention may be required to resolve conflicts.
It is an object of the present invention to obviate or mitigate some of the above disadvantages.